1. Field of the Invention
The production of a synthesis gas in the normal gasifier usually embodies the partial oxidation of a fuel mixture at a relatively high temperature. The resulting products, when the fuel includes a solid carbonaceous ingredient such as ground coal or coke, will include the desired synthesis gas, together with an amount of uncombusted effluent.
-When the fuel mixture is comprised as noted of a carbonaceous material, such as coal or coke, the composition of the latter can be such that varying amounts will remain uncombusted and will consequently be passed through the gasifier or circulated in the combustion chamber and remain a solid. While a considerable amount of the solid component will be carried into the gasifier's quench chamber, at least a portion will be retained, and cling to the combustion chamber walls where it forms a slag.
When in a plastic state, the slag will gradually flow by gravity down the gasifier combustion chamber walls to the water bath; it will, however, eventually solidify at such time as the unit is closed down or the temperature of the combustion chamber is reduced below the slag melting point.
At some point in the syngas production process, it will be apparent that the presence of an excessive amount of slag within the gasifier is impeding or will impede the gasification process. Prudent and economic practice dictates that at this point, the unit be shut down for the specific purpose of removing the slag. This is achieved by a melting or a deslagging operation, which embodies adjusting the gasifier to a sufficiently high temperature to melt the slag, and/or adding an oxidizer.
2. Discussion of the Prior Art
Processes applicable to the deslagging of gasifiers as a practical matter usually embody the primary step of heating the combustion chamber sufficiently to convert hardened or solidifed slag into flowable condition. An illustration of such a process is disclosed in U.S. Pat. No. 4,525,176, Kogg, et al. The claimed deslagging process is carried out by introduction of a variable fuel mixture into a gasifier combustion chamber where slag has accumulated. A deslagging burner is physically adjustable in the combustion chamber to improve the distribution of heat.
In simple terms, the deslagging operation or phase consists of injecting a combustible gas or liquid fuel mixture into the gasifier combustion chamber from either a burner particularly adapted to the purpose or from the process burner. The flow of fuel gas or gas mixture is normally monitored to assure a high enough temperature and oxygen partial pressure that the slag will be effectively fluidized and flow from the combustion chamber. The combustion chamber walls will then be substantially free of slag which could otherwise impede continuation of the syngas manufacturing process. It is found to be desirable through practice, however, that rather than completely removing all slag, a minor amount can be retained on the combustion chamber walls as a corrosion preventive or inhibiting measure for the refractory lining.
A burner of the type utilized in a deslagging operation may differ from the normal syngas process burner. Further, the flow of gas or liquid from the deslagging burner into the combustion chamber is preferably metered such that the most effective fuel mixture is formed and enters the combustion chamber to be immediately ignited and to eventually raise the chamber to a desired temperature level and oxygen partial pressure.